In this week's Science, they report that pollen and spore counts in the sediment core show a jump in the number of ferns at the time of the meteor impact. Ferns can grow in harsh conditions, and 'fern spikes' where other plants are scarce are recognised as evidence of catastrophic ecosystem disruption.

The sediments also showed a higher-than-normal level of iridium, a 'signature' of the meteor impact.

"The pollen from this remote location speak eloquently of ecological devastation on the same order as in North America," said Dr Tim Flannery, Director of the South Australian Museum, in a discussion paper in the same issue of Science.

The sediments were from a mine on the west coast of New Zealand's South Island, about 11,000 km from where the meteor hit in Mexico  "about as distant from the site of the impact as it is possible to be", Flannery writes.

The meteor was a relic from the formation of the solar system, about 10 km in diameter. It hit the Earth at about 90,000 km per hour, sparking massive wildfires.

The thermal radiation from meteor parts entering the atmosphere probably also caused other wildfire outbreaks worldwide.

In addition, huge amounts of dust would have been blasted into the atmosphere, causing an 'impact winter', similar to a nuclear winter, with sunlight unable to penetrate. With no heat or light for photosynthesis, plants and animals would have perished.

The meteor is thought to have hit the Earth on a tangent, causing far more damage than if it had been a straight impact because of the amount of debris dislodged into the atmosphere.

Ecological damage in North America has been well documented and conventional thinking was that the extent of damage suffered by North America was unique. Though Australasian dinosaurs and reptiles suffered the same extinctions as those of the Northern Hemisphere, there has previously been little evidence of devastation of entire ecosystems in the Southern Hemisphere.

If isolated New Zealand suffered similar effects to North America, then the meteor must have been felt worldwide, the authors argue.

Dr Flannery states that further evidence from other Southern Hemisphere continents is required to confirm the theory.